The man also pleaded guilty to an unrelated charge of driving while disqualified.
Judge Glubb sentenced the man on the spot to one month in prison and disqualified him from driving for nine months. He noted it was the man's ninth disqualified driving offence.
At the end of the hearing, the man said "thank you, your honour'' and appeared to mouth a kiss at his sole supporter in the small courtroom.
Police earlier said officers had searched the man's property and seized a car believed to be relevant to the investigation.
Detective Senior Sergeant Grant Ferguson said an investigation team had been engaging with the community and collecting evidence and information.
An alleged offender had also been captured on CCTV footage at the storage unit and appeared to have changed clothing to avoid detection.
"It is pleasing to be able provide the large number of victims who have lost many valuable items, both in the monetary and sentimental sense, with the reassurance that someone will be held accountable for this arson,'' Mr Ferguson said.
Police were still seeking sightings of a light blue 1994 Daihatsu Charade which was in the suburbs of Johnsonville and Kilbirnie, particularly around the storage unit, between 12am and 1am on Friday, April 4.
"We continue to seek the public's assistance with this investigation as I believe they will hold valuable information about the movements of the offender on the night of the fire,'' Mr Ferguson said.
Image 1 of 17: Smoke billowing from the Kiwi Storage facility as firefighters struggle to control the blaze near Wellington Airport. Photo / Mark Mitchell
